Making a rigable robot
Unless you have good reasons to keep some meshes separate (like a modifier that must not affect the other meshes), it would be simpler to join them.

For the second question, it really depends on what you want, it will deform but it won't necessarily be a problem so you should try this solution, on this topic you can follow this very simple tutorial by AgenZasBrothers that explains how to create robot limbs with Array and Curve modifiers, maybe at the end parent the vertices to bones so that you can always come back to a Rest pose.

Also maybe this answer I gave on how to rig a cartoon-like limb may interest you.